Atmospheric Circulation – some basics of the large scale circulation of the atmosphere along with the lapse rate (temperature profile in the atmosphere), potential temperature

Back Radiation – a three part series on the often misunderstood subject of radiation emitted by the atmosphere, followed by a four part series on whether this atmospheric radiation can increase the temperature of the ocean

The Hoover Incident – what the earth’s climate might be like if all of the gases like CO2 and water vapor were “hoovered up” so that the atmosphere didn’t absorb or emit any radiation

Simple Atmospheric Models – Part One and Part Two – explaining a couple of simple atmospheric models, introduced with mendacious intent by climate scientists to confuse the good citizens of the blogosphere, knowing that they will never actually read their textbooks

How “Greenhouse” Gases affect the Atmosphere, Is CO2 Insignificant, Is CO2 Saturated and Everything Else you Ever Wanted to Know

and also see the series Back Radiation – a three part series on the often misunderstood subject of radiation emitted by the atmosphere, followed by a four part series on whether this atmospheric radiation can increase the temperature of the ocean

I see in your roadmap you have about the physics of radiation absorption and re-emission and an exploration of Global Climate Models.

I am quite comfortable with the basic physics of the ‘greenhouse’ effect.

What I am very uncomfortable with is how good the GCM theoretical models are and how they account for feedback. I understand they assume a positive feedback process – though I would call it an amplification process: true positive feedback would be disastrous. History however shows the earth’s climate to range between narrowly constrained temperatures. To me this is indicative of a strong negative feedback process against most forcings – Solar radiation, orbital changes, atmospheric composition etc.

Can I ask you to include a section looking at the feedback processes – both those assumed by the GCMs and those that can be inferred by historical records?

Could you also explore falsifiability of the GCMs? What is the present state of proving or otherwise the GCMs?

Your position, your questions nicely sum up the informed side of the “skeptics”, if I can use a label which I also apply to myself.

The GCMs don’t assume a positive feedback. They throw all the known climate’s physics laws and parameterizations of those laws into a model, throw in the current conditions and see what comes out the other side. Well, I don’t mean to write off many people’s life’s work by that throwaway line..

What the climate history shows is food for both sides of the debate which is what makes it so fascinating. If it was solely negative feedback we would probably see minor perturbations around a gradually moving average temperature (as much as it can be reconstructed). But we see sharp up and down movements.

If it was solely positive feedback the planet would be burning or frozen.

And why, as you rightly say, does the temperature not move too much from one fairly tight range?

One other area that appears to me to be totally hand-waving and idle speculation is ‘orbital forcings’

My background includes quite a few years working as an oceanographer with tides and tidal currents. For me, these are easily understood and are very predictable – literally. Tides must be one of the most predictable phenomena on earth. I can tell you exactly how high the tide was when Kind Canute did his holding-back-water trick – that is if you can tell me precisely when and where it happened.

Tides, as you realise, are completely the results of short period orbital forcings.

So when I see an irregular interval of ice-ages and general hand-waving about ‘100,000 year milankovitch cycles’ I smell a rat.

We should know precisely what the orbital parameters were over a very long period. We should also be able to work out exactly how much energy was flowing into the earth as a result of these changes.

Some exploration of what the actual orbital forgings were compared to the climate record would be very interesting.

I am interested in cycles. It is very evident that similar cycles periods are found in solar proxies and climate proxies. This applies to long cycles such as de Vries 2300 years, medium like Halstatt 208 years, and perhaps something around 55-60 years which fits with temperature extremes of ~1910 low, ~1940 high, ~1970 low, ~1998 high.

To me this is strong evidence that solar fluctuations are a principle factor in climate fluctuations. Any human / CO2 effects must surely be studied against this backdrop of know cyclical solar behaviour?

If Nasif Nahle isn’t just an extreme outlier, then I think you may need a part 9 for CO2 – An Insignificant Trace Gas? to go into more detail on calculating atmospheric radiative emission, specifically the effect of path length. I’ve tried in Lunar Madness and Physics Basics, but I’m not very good at simplification for the masses.

I think you did just fine explaining it. But I was wondering whether it made sense to write an article on this topic and bring a few points together.

I think Nasif Nahle is an outlier, but there are a few people showing up now and again thinking that Hottel and Leckner are the real deal while RM Goody and the many afterwards in atmospheric radiation just don’t understand the subject. Of course, Leckner does refer people to RM Goody for atmospheric radiation..

If you use the right path length, Hottel and Leckner will get you in the ballpark. So I don’t think it’s really about them vs Petty or Goody, it’s about understanding the basic principles of atmospheric radiative emission. You did a good job on the absorption part, but let the emission part slide a little.

I’ve found an email address for Bo Leckner. I think I’ll write him and see if he is willing to put this to rest.

First, thank you for a very illuminating blog.
Secondly, my apologies if this comment/question is in the wrong place, I couldn’t see anywhere appropriate to place it.
A back of the envelope calculation on the heat released from fossil fuels over the past 50 years or so (50*ave. fossil fuel mass p.a.*ave. heat of combustion) gives approximately 1*10^22joules. Applying this to the total mass of the atmosphere (5*10^21 grammes) would give a temperature rise of 2 degs. K in the atmosphere. Assuming efficiencies of energy use of say 40 % would still give sufficient heat for a temperature rise of 1.2 degs.
Other than a paper by Bo Nordell last year (2009) I have difficulty in finding much in the literature on this type of approach (I’m retired so don’t have exhaustive facilities). Is there a simple reason why this energy is ignored?

In the first case (burning fossil fuels) you have added a fixed amount of heat: X joules over a time period.

In the second case (adding CO2) you have added a radiative forcing: Y W/m^2.

We can work out a comparison at a very simplistic level to give us an idea whether they are comparable – or whether one is “out of sight” compared with the other.

The comparison – if we use your value of heat added (the first case) –

10^22 Joules / 50 years = 10^22/(50*365*24*3600) = 6.3×10^13 W

So what does that equate to in terms of W/m^2?

Surface area of the earth = 5.1×10^8 km^2 = 5.1 x10^14 m^2

Heat added per sec per m^2 = 6.3×10^13 / 5.1×10^14 = 0.12 W/m^2.

Of course it’s not as simple as this, but it gives a rough idea of magnitude compared with the current forcing compared with pre-industrial levels of “greenhouse” gases of around 2.4 W/m^2.

I don’t know whether your original number was correct. And the radiative forcing (all other things being equal) for CO2 has increased from the 19th century to the present day. If CO2 and other GHG forcing had increased linearly then you could halve that value to account for the change over the last 100+ years.

With your numbers it looks like the radiative forcing is around 10x the heat added when we compare with similar units. This indicates that it is worth looking more closely.

I think it should be 6.3*10^12 rather than 10^13, which means the difference in magnitude is 100-200 times.
I guess I’m battling to absorb the dynamics of the radiation forcing, since if I turn the discussion on its head,and use the figures (ex wikipedia) for 2007, I get 3*10^20 W (or 0.02W/m2) which could heat the earths atmosphere by 0.06 deg. An effect 100+ greater than this would be capable of heating the whole of the earths atmosphere by 1 degree every 2 months. I know you’ve warned against pictures (intuition?) versus the maths but still have difficulty with all the energy being dumped into the water/land heat sink or radiated into space.
Thanks for your attention

If you have a system in balance and you change the conditions slightly so more heat is going in than out then perhaps it will increase in temperature forever?

No it won’t. The temperature will increase until the system moves back into balance. Higher surface temperatures increase radiated heat.

The same is true of any other heat transfer mechanism. Increase the heat into one side of a metal plate when the other side is held constant. What happens? Does the metal plate heat up forever? No. The temperature increases until the conducted heat through the plate matches the incoming heat – at which point it is back in balance.

Just discovered this site and have spent about 8 hours thus far gobbling up topics. I like the approach very much and it appears to be rich in the needed physics and climate science. I’m especially grateful for the MATLAB code – after reading your pieces on the radiation basics.

I have a question on the effects of CO2 content but want to first disclose that my reading is limited thus far to Ian Plimer’s “Heaven and Earth …”, Svensmark’s work via his book, the paper by Gerlich & Tscheuschner, blogs such as WUPT, pieces of the EPA’s endangerment assessment and plenty of videos, including several featuring Lindzen. My background is EE, (Maxwell equations), etc. and I’m just getting back up to speed on thermodynamics via my physics handbook.

So, here’s the question: My understanding is that CO2 content beyond a couple hundred ppmv “doesn’t add much to this thing they call ‘Global Warming Potential'”. Some of the statements on this appear to infer that regardless of the (CO2-tuned) radiant flux input CO2 can’t handle any more – even if it’s doubled. This doesn’t make sense to me. It makes sense if the interpretation is that the average radiant flux input just doesn’t go much beyond what we’ve experienced, say, just this past century and thus the additional CO2 is ready to handle radiant flux that just isn’t going to get much greater on average. Which is correct … or is there an alternate explanation? (I know. I should move on and read your posts on this subject, but I may not get around to that as quickly as I’d like).

A new paper proving that CO2 is a minor player in the drama that is the Earth’s climate.

Abstract

We present here a simple and novel proposal for the modulation and rhythm of ice ages and interglacials during the late Pleistocene. While the standard Milankovitch-precession theory fails to explain the long intervals between interglacials, these can be accounted for by a novel forcing and feedback system involving CO2, dust and albedo. During the glacial period, the high albedo of the northern ice sheets drives down global temperatures and CO2 concentrations, despite subsequent precessional forcing maxima. Over the following millennia CO2 is sequestered in the oceans and atmospheric concentrations eventually reach a critical minima of about 200 ppm, which causes a die-back of temperate and boreal forests and grasslands, especially at high altitude. The ensuing soil erosion generates dust storms, resulting in increased dust deposition and lower albedo on the northern ice sheets. As northern hemisphere insolation increases during the next Milankovitch cycle, the dust-laden ice-sheets absorb considerably more insolation and undergo rapid melting, which forces the climate into an interglacial period. The proposed mechanism is simple, robust, and comprehensive in its scope, and its key elements are well supported by empirical evidence.

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